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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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 * accompanied this code).

 *

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package javax.lang.model.util;

import javax.lang.model.type.*;

/**

 * A skeletal visitor of types with default behavior appropriate for

 * the {@link javax.lang.model.SourceVersion#RELEASE_6 RELEASE_6}

 * source version.

 *

 * <p> <b>WARNING:</b> The {@code TypeVisitor} interface implemented

 * by this class may have methods added to it in the future to

 * accommodate new, currently unknown, language structures added to

 * future versions of the Java™ programming language.

 * Therefore, methods whose names begin with {@code "visit"} may be

 * added to this class in the future; to avoid incompatibilities,

 * classes which extend this class should not declare any instance

 * methods with names beginning with {@code "visit"}.

 *

 * <p>When such a new visit method is added, the default

 * implementation in this class will be to call the {@link

 * #visitUnknown visitUnknown} method.  A new abstract type visitor

 * class will also be introduced to correspond to the new language

 * level; this visitor will have different default behavior for the

 * visit method in question.  When the new visitor is introduced, all

 * or portions of this visitor may be deprecated.

 *

 * <p>Note that adding a default implementation of a new visit method

 * in a visitor class will occur instead of adding a <em>default

 * method</em> directly in the visitor interface since a Java SE 8

 * language feature cannot be used to this version of the API since

 * this version is required to be runnable on Java SE 7

 * implementations.  Future versions of the API that are only required

 * to run on Java SE 8 and later may take advantage of default methods

 * in this situation.

 *

 * @param <R> the return type of this visitor's methods.  Use {@link

 *            Void} for visitors that do not need to return results.

 * @param <P> the type of the additional parameter to this visitor's

 *            methods.  Use {@code Void} for visitors that do not need an

 *            additional parameter.

 *

 * @author Joseph D. Darcy

 * @author Scott Seligman

 * @author Peter von der Ahé

 *

 * @see AbstractTypeVisitor7

 * @see AbstractTypeVisitor8

 * @since 1.6

 */

public abstract class AbstractTypeVisitor6<R, P> implements TypeVisitor<R, P> {

    /**

     * Constructor for concrete subclasses to call.

     */

    protected AbstractTypeVisitor6() {}

    /**

     * Visits any type mirror as if by passing itself to that type

     * mirror's {@link TypeMirror#accept accept} method.  The

     * invocation {@code v.visit(t, p)} is equivalent to {@code

     * t.accept(v, p)}.

     *

     * @param t  the type to visit

     * @param p  a visitor-specified parameter

     * @return a visitor-specified result

     */

    public final R visit(TypeMirror t, P p) {

        return t.accept(this, p);

    }

    /**

     * Visits any type mirror as if by passing itself to that type

     * mirror's {@link TypeMirror#accept accept} method and passing

     * {@code null} for the additional parameter.  The invocation

     * {@code v.visit(t)} is equivalent to {@code t.accept(v, null)}.

     *

     * @param t  the type to visit

     * @return a visitor-specified result

     */

    public final R visit(TypeMirror t) {

        return t.accept(this, null);

    }

    /**

     * Visits a {@code UnionType} element by calling {@code

     * visitUnknown}.

     * @param t  {@inheritDoc}

     * @param p  {@inheritDoc}

     * @return the result of {@code visitUnknown}

     *

     * @since 1.7

     */

    public R visitUnion(UnionType t, P p) {

        return visitUnknown(t, p);

    }

    /**

     * Visits an {@code IntersectionType} element by calling {@code

     * visitUnknown}.

     * @param t  {@inheritDoc}

     * @param p  {@inheritDoc}

     * @return the result of {@code visitUnknown}

     *

     * @since 1.8

     */

    public R visitIntersection(IntersectionType t, P p) {

        return visitUnknown(t, p);

    }

    /**

     * {@inheritDoc}

     *

     * <p> The default implementation of this method in {@code

     * AbstractTypeVisitor6} will always throw {@code

     * UnknownTypeException}.  This behavior is not required of a

     * subclass.

     *

     * @param t  the type to visit

     * @return a visitor-specified result

     * @throws UnknownTypeException

     *  a visitor implementation may optionally throw this exception

     */

    public R visitUnknown(TypeMirror t, P p) {

        throw new UnknownTypeException(t, p);

    }

}